This invention relates to a fabric softening agent and to a liquid detergent laundering product including the softener. The detergent contains one or more anionic, nonionic, and cationic surfactants.
Solid detergent formulations are sold in powder or granular form. A disadvantage of solid detergents is that, on account of the hygroscopicity of individual raw materials of the formulation, the solid detergent shows a pronounced tendency towards caking or clumping in the presence of small quantities of moisture. This does not make the detergent unusable, however, because the effect of the individual components of the detergent remain intact even after clumping or caking in the presence of moisture. However, the appearance of the detergent in most cases is diminished. As a result, there has been a desire to develop liquid detergent compositions for convenience in lieu of conventionally formulated solid detergent compositions. The liquid detergent allows for use of lower washing temperatures inclusive of cold water laundering. Granular detergents have not fully adapted to such variations because of weaknesses in respect of dissolving speed, insolubility, and cleaning efficiency. Due to such problems of caking and the slowness of solid and granular detergents to dissolve, trends in detergent manufacture have leaned toward the liquid detergent. Such detergents usually include one or more anionic, nonionic, and cationic organic surfactants, water, brightening agents, hydrotropes, enzymes, soil suspending agents, bleaches, pH modifiers, and solvents. It is not uncommon to also include an antifoam or defoamer formulation as a part of the detergent package. Such systems may be built or free of builders.
A fabric softener often contains a dilute solution or dispersion of a quaternary ammonium derivative used to treat fabrics in the final rinse of a laundering process in order to make the fabrics feel softer. In addition to softness, fabric softeners are known to also provide static control. Because of the affinity of quaternary ammonium compounds for negatively charged surfaces, their single largest market has been as fabric softeners. Commercial fabric softeners generally include about a four to eight percent dispersion of quaternary ammonium compound which is added to the rinse cycle of the washing process. In some cases, a fatty acid stearate is added to modify the handle. The quaternary ammonium compound can also be applied to a nonwoven sheet or a polyurethane foam which is added with wet clothes in a dryer. Such sheets contain a fatty amine or a fatty acid ester which allows the quaternary ammonium compound to transfer from the sheet to the clothes in the dryer during the drying cycle. Recently, there have been devised combined detergent and softener formulations which allow introduction of all additives in the wash cycle.
A basic distinction should be drawn between a rinse cycle softener and a wash cycle softener. As noted hereinabove, the rinse cycle fabric softener is a liquid dispersion of a quaternary ammonium compound which is added separately to the rinse liquor during the rinse cycle of the laundering device. A wash cycle fabric softener on the other hand typically contains the quaternary ammonium compound which is mixed in with the laundry detergent and added to the wash liquor by the homemaker, for example, before initiation of the wash cycle of the fabric laundering device. Wash cycle softeners often also include mixtures of quaternary ammonium compounds, clays, and amines.
The present invention relates to this latter category of softener, or specifically to a liquid wash cycle softening detergent. Liquid detergents containing silicone fabric softening agents are not new as exemplified by U.S. Pat. No. 4,639,321, issued Jan. 27, 1987. The 321 patent describes a liquid detergent having through-the-wash softening benefits comparable to the softening obtained with cationic rinse cycle softener formulations. In addition to anionic and nonionic surfactants, and a carrier, this softening liquid detergent is said to contain an aminosubstituted polydialkysiloxane as the softening agent. However, such aminofunctional siloxanes suffer from the disadvantage in that such compounds tend to yellow fabrics.
In an effort to avoid this disadvantage of the aminofunctional type materials of the prior art, the present invention is directed to a liquid detergent having fabric softening properties and including a particular category of polyorganosiloxane which is free of reactive functional groups. However, because polydimethylsiloxane is very insoluble in water, it is difficult to produce stable products containing these materials such as required in liquid detergent systems. This is for the reason that the polydimethylsiloxane molecule does not include hydrophilic groups which would render the molecule more compatible in typical liquid detergent formulations. Nevertheless, surprisingly it has been discovered that by properly emulsifying these reactive free silicones in a detergent matrix, that the polydimethylsiloxane can be rendered compatible in a liquid detergent system. This is significant since polydimethylsiloxanes are not known to possess the characteristic yellowing property of aminofunctional poiyorganosiloxanes. Thus, and in accordance with the concepts of the herein described invention, there is set forth a new and novel liquid detergent having fabric softening and cleaning properties and which contains as the softening agent a non-yellowing type of silicone.